My little children - The language of tender affection, such as a parent would use toward his own offspring; see the note at 1 Corinthians 4:15; compare Matthew 18:3; Joh 13:33; 1 John 2:1, 1 John 2:12-13; 1 John 4:4; 1 John 5:21. The idea here is, that Paul felt that he sustained toward them the relation of a father, and he had for them the deep and tender feelings of a parent.
Of whom I travail in birth again - For whose welfare I am deeply anxious: and for whom I endure deep anguish; compare 1 Corinthians 4:15. His anxiety for them he compares to the deepest sufferings which human nature endures; and his language here is a striking illustration of what ministers of the gospel should feel, and do sometimes feel, in regard to their people.
Until Christ be formed in you - The name Christ is often used to denote his religion, or the principles of his gospel; see the note at Romans 13:14. Here it means, until Christ reigns wholly in your hearts; until you wholly and entirely embrace his doctrines; and until you become wholly imbued with his spirit; see Colossians 1:27.